The regulation in force relating to lift apparatuses (Directive 95/16/EC) provides that all lift apparatuses have overspeed safety systems for the purpose of assuring people's safety. These protective means must act in the moment in which the apparatus reaches a speed exceeding the nominal speed by a magnitude provided under the regulation for the car traveling both in the upward and downward direction, completely stopping the car.
As a result of this regulation, lifts conventionally have a speed governor usually located in the machine room, or recently in the upper part of the elevator shaft in the event of not having a machine room. Said speed governor comprises a sheave sharing the same axis of rotation and through which a segment of rope passes, the ends of which rope are joined to the car, such that the rope is tensed by a second sheave arranged in the pit of the elevator shaft. In the moment in which the car exceeds the established speed limit, the speed governor acts on the safety gear located in the car frame, such that the safety gear stops the car by friction.
The latest technological advances in the field of the speed governors have focused on reducing the necessary space occupied by these devices with the objective of optimizing the efficiency of the shaft, simplifying the assembly and facilitating maintenance. This translates into recent new inventions in which the governor rope as well as the corresponding tension sheave are eliminated, such that the speed governor is a rider associated to the car and acts on the safety gear by means of different intermediate mechanisms.
The known state of the art includes patent ES 2184612 describing a centrifugal speed governor rider on the car acting on the safety gear by means of a set of levers forming a four bar linkage. The overspeed detection device obtains the rotating speed through contact of a disc with the guide rail on which the car travels. In the moment of activation, the speed governor locks up and by means of the force of friction generated between the disc and the guide rail, movement of the four-bar linkage which in turn acts on the safety gear begins.
Patent EP 0475114 describes a safety device rider on the car combining a centrifugal force speed governor with the safety gear by means of a conventional set of levers. Like the previous invention, the activation force of the safety gear is established by the friction between the rotating element associated to the governor and the guide rail.
U.S. Pat. Nos. 4,662,481, 5,377,786 and WO 03070615 describe inventions which, like the previous documents, combine a centrifugal force speed governor associated to the car with the safety gear by means of different intermediate mechanisms, usually sets of conventional levers, obtaining the car traveling speed through contact with the guide rail on which it travels, such that the activation force of the safety gear is established by the friction existing between these two elements.
All these inventions share the need of having an intermediate mechanism between the overspeed detection device (usually called the speed governor) and the safety gear. They also need to have means for assuring suitable friction between the guide rail and the disc belonging to the overspeed detection device, since the activation force of the safety gear is established by said contact. Particular care must be taken with this aspect, since the guide rails are susceptible of being impregnated with different chemical agents, such as lubricants, oils, etc., necessary either to favor the car guiding system or for maintenance of the traction ropes, being able to affect the contact between guide rail and speed governor. Both the intermediate activation mechanism and the means for assuring suitable contact between disc and guide rail limit the space required for the safety system formed by the speed detection device, the actuating device and the safety gear.
In the field of the art comprising the present invention, it is known that any improvement in reducing the necessary space occupied by the safety system, as well as reducing the number of parts forming it, involves a technological advance.